1. Field of the Invention
The present invention relates to a gas laser oscillator which has the function of judging the start of discharge.
2. Description of the Related Art
There is a gas laser oscillator known, in which a voltage which is supplied to a discharge tube is detected and it is judged if a discharge in the discharge tube has started based on the detected value. For example, in the gas laser oscillator described in Japanese Unexamined Patent Publication No. 2011-222586A (JP2011-222586A), the output command value to the laser power supply is increased in steps. Further, the difference between a ratio of change of a detected value of a discharge tube voltage relative to a power output command value and a ratio of change of a discharge tube voltage relative to a power output command value determined in advance based on data when normally discharging is determined, and judges that the discharge has started when that difference becomes within a predetermined threshold value.
In this regard, in a gas laser oscillator, changes in the pressure, flow rate, composition, and other states of the laser gas which circulates inside the discharge tube sometimes make start of discharge difficult. Therefore, if, like in the gas laser oscillator described in JP2011-222586A, increasing the power output command value in steps until the start of discharge is judged, an excessive current flows to the laser power supply, as a result, an overcurrent prevention circuit, etc. is liable to function and start of discharge is liable to be hindered.